Displacement reactions involving the halogens
2 marks · HardState and explain the trend in the reactivity of chlorine, bromine and iodine as shown by their displacement reactions.
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Also accept: Reactivity decreases down the group; chlorine is most reactive, bromine is less, iodine is least. More reactive halogens displace less reactive ones from salts.
Common mistakes: States trend but gives wrong order; does not link to displacement.
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Marking points
B1 · 1 mark · States reactivity decreases down the group (or gives correct order: chlorine > bromine > iodine).
B2 · 1 mark · Explains that a more reactive halogen can displace a less reactive one from its salt.
Worked solution
The reactivity of the halogens decreases as you go down the group: chlorine is most reactive, then bromine, then iodine. This means only a more reactive halogen can displace a less reactive one from its salt.